low mileage

I have 95 4 runner 4wd. it does about 12 in city and 14 on hwy. Also what looks like it takes long time for it to shift in to high gear when you going 35 to 40 mph. On highway going 65 mph to slightest up hill it will down shift in to low gear and stay there until I tap on accelerator. Is this all normal, or is there fix to it?

 

when was the last time that you had the transmission serviced? it the vehicle it staying in a lower gear, it is running at higher RPMs, thus burning more fuel.